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Silica mixing for landscape evolution experiments

Crystalline silica flour was mixed with water to serve as the experimental substrate for landscape evolution experiments at the XLE facility at St. Anthony Falls Laboratory. Mixing the sediment with water reduces infiltration and increases material cohesion.

Handling this material requires a half-face respirator and full PPE; check with your institution's Health and Safety office for specific containment and material handling policies.

The experimental flume accommodates ~ 6 50-lb bags of silica. Sediment was mixed in three batches in a standard rotating cement mixer, fitted with a cover to reduce dust. Each batch consisted of two bags of silica and 13 L of water. Sediment was added to the mixer one bag at a time to increase the homogeneity of the mix. Once all the sediment was added, the batch was mixed for ~2 hours, stopping every 30 minutes to incorporate dry bits of sediment and break up clumps. After mixing, each batch was loaded into the XLE and patted into place to break up remaining clumps and fill the corners of the box. Once the box was full, sediment was allowed to settle for 24 hours to reduce air bubbles and enable excess water to come to the surface. This water was drained off the surface before beginning the experimental run.